Make sure that you have a working network connection then
proceed to the next steps.

Synchronize your package database.

pacman -Syy

Now lets install ntchpw.

pacman -S chntpw

It is now time to mount the Windows drive. The command below
assumes that your Windows C:\ drive is at /dev/sda1, but it
might not be the case with your setup. Check fdisk(8) and lsblk(8)
to see which is the correct device of your Windows systems.

mount /dev/sda1 /mnt

The Windows SAM file location by default is at
C:\Windows\System32\config, so lets navigate to that directory first.

cd /mnt/Windows/System32/config

List the local users from the SAM file by executing the command below.

chntpw -l SAM

Select the user you wish to reset/unlock and run the following
command.

chntpw -u <user> SAM

From there on simply follow the menu instructions provided by
chntpw and you should be ready to go.